In recent years, an electric vehicle driven by electric power, such as an electric vehicle (EV) with a storage battery and a plug-in hybrid vehicle (PHV), has been practically used. Such electric vehicle has an in-vehicle charger that receives electric power from an external power source, such as a commercial 100 Vac power source, to charge a built-in battery for traveling. Herein, if an electric leakage occurs on the vehicle side when the battery is charged, an excessive current may flow into the in-vehicle charger. Therefore, a power supply control device is used for intercepting the power supply to the electric vehicle when the leakage occurs (e.g., see Japanese Patent Application Laid-open No. 2009-240053).
FIG. 11 is a block circuit diagram of a power supply control device 101. The power supply control device 101 is configured to accommodate a relay 2, a zero-phase current transformer 3, a control circuit 4, and a power circuit 5 within a housing 110 (see FIG. 12). The power supply control device 101 is provided with a power side plug P1 connected to an external power source, and a vehicle side plug P2 connected to an in-vehicle charger in a vehicle. These plugs P1 and P2, and the circuits in the housing 110 are connected via cables C1 and C2. Now, the cable C1 between the power supply control device 101 and the power side plug P1 includes two power wires L1 and L2, and a ground wire L3. Further, the cable C2 between the power supply control device 101 and the vehicle side plug P2 includes the above three wires L1 to L3 and an electric wire L4 for transmitting signals to and from the in-vehicle chargers.
The relay 2 has relay contacts 2a provided in internal conductive lines connected to the power wires L1 and L2, respectively, and the control circuit 4 controls ON/OFF operations of the relay contact 2a. 
The zero-phase current transformer 3 is used for detecting an unbalanced current that flows through the power wires L1 and L2 when the leakage occurs.
The control circuit 4 opens or closes the relay 2 based on control signals inputted from the in-vehicle charger of the electric vehicle via the electric wire L4, so that the power supply to the in-vehicle charger is turned off or on. Besides, when detecting the unbalanced current flowing through the zero-phase current transformer 3, the control circuit 4 opens the relay 2 to cut off the leak current flowing into the electric vehicle.
The power circuit 5, to which an electric power is supplied from the external power source, supplies the electric power to the control circuit 4.
The housing 110 of the power supply control device 101, as shown in FIG. 12, includes a body 111 with a rectangular parallelepiped shape of which one side is opened, and a cover 112 attached to the body 111 so as to cover the opening of the body 111. The relay 2, the zero-phase current transformer 3, the control circuit 4, and the power circuit 5, which are described above, are accommodated in an inner space defined by the body 111 and the cover 112. In opposite side walls of the body 111 in its longitudinal direction (up and down side walls in FIG. 12), joint portions with the cover 112 are each recessed to provide a cable passing port 17 for introducing the cable C1 or C2.
By the way, in view of wet circumstances in an outdoor parking space, the power supply control device 101 requires high waterproof performance. Higher waterproof performance needs complete sealing of the housing 110. The housing 110 is, however, configured to be opened and closed for replacement of the cables C1 and C2 when they are broken by, e.g., a vehicle passing over them. Each of the cables C1 and C2 introduced into the housing 110 is connected to a terminal box disposed within the housing 110 to be electrically connected to the internal circuit. On the other hand, the cables C1 and C2, which are connected to the respective terminal boxes, are extended to outside through the respective cable passing ports 17. Therefore, it becomes necessary to prevent, e.g., rain water from infiltrating into the housing 110 through the cable passing ports 17. Accordingly, in the power supply control device 101 disclosed in the above-cited reference, a gasket 50 provided on each of the cables C1 and C2 is attached to the cable passing port 17 to seal a gap between the body 111, the cover 112, and the cables C1 and C2.
The gasket 50, as shown in FIG. 13, has: a cylinder part 51 surrounding the cables C1 and C2; and a couple of flanges 52 and 53 protruding outwardly from the cylinder part 51 and sealing the gap between the body 111, the cover 112, and the cables C1 and C2. Further, in order to make the cylinder part 51 flexible, a plurality of annular grooves 54 extending circumferentially is formed on the cylinder part 51 at predetermined intervals in an axial direction thereof.
In the power supply control device with such configuration, the gasket 50 provided on each of the cables C1 and C2 is attached to the cable passing port 17 for the purpose of ensuring waterproof performance of the housing 110. When the cable C1 or C2 is bent in directions denoted by arrows A1 and A2 in FIG. 13A, the gasket 50 is hardly bent in conformity with the bending of the cable C1 or C2. This may cause a gap between an outer surface of the cable C1 or C2 and the gasket 50, which deteriorates the waterproof performance.